1. Field of the Invention
The invention relates to an improved blood pressure monitoring device in which the pump, valve and transducer are located on the cuff which surrounds a patient's arm.
2. Description
Automatic blood pressure measuring devices for measuring a patient's blood pressure in certain intervals over an extended period of time or upon manual initiation by the patient or the medical staff are known for a long time either for stationary or ambulatory purposes. For ambulatory use it is necessary that the device is small and lightweight and contains a data storage system. A further major requirement for all blood pressure measuring devices is the reduction or elimination of artefacts due to relative movement between patient and recording device.
In all blood pressure measuring devices known up till now a cuff surrounding the patient's arm is connected via a hose to a module containing the pressurizing system and the signal processing circuitry. In the classical embodiment a second hose is connected between a transducer which is also contained in the module and the cuff to measure the cuff pressure. A valve is connected to the pressurizing system between the pump and cuff.
According to a more recent development the pressure transducer is also connected to the pressurizing system between the pump and the cuff so that the second hose could be eliminated. Still the connection between the module and the cuff is affected by the hose supplying or withdrawing the air or gas for inflating or deflating the cuff.
It has been discovered that this configuration causes considerable artefacts resulting in inaccurate or unstable readings due to the movement of the hose in case of relative movement of the patient with regard to the module. A further disadvantage resides in the significant portion of dead volume which has to be pressurized during inflation of the cuff and which requires oversized pumps.
The present invention provides a blood pressure measuring device for ambulatory purpose which generates less artefacts and exhibits a lower dead volume than the devices known to date.